Hi, I prefer to use bCache or other likely local write back cache on SSD since it is only related to local HDDs. It think, it will reduce the risk of error on cache flushing comparing to CEPH Cache Tiering which still using clustering network on flushing. After the data has been written to the cache of an OSD, that OSD has done the writing process and the rest is internal OSD process. Anyway, the performance testing report will be so interesting. Best rergards, > Date: Tue, 8 Jul 2014 09:40:29 +0000 >> From: Somhegyi Benjamin <somhegyi.benjamin at wigner.mta.hu> >> To: Arne Wiebalck <Arne.Wiebalck at cern.ch>, James Harper >> <james at ejbdigital.com.au> >> Cc: "ceph-users at lists.ceph.com" <ceph-users at lists.ceph.com> >> Subject: Re: [ceph-users] Using large SSD cache tier instead of SSD >> journals? >> Message-ID: >> < >> C8C8E269282A034CA2A0180CBE01C24001B625A4 at WDCSRV.wdc.wigner.mta.hu> >> Content-Type: text/plain; charset="us-ascii" >> >> Hi Arne and James, >> >> Ah, I misunderstood James' suggestion. Using bcache w/ SSDs can be >> another viable alternative to SSD journal partitions indeed. >> I think ultimately I will need to test the options since very few people >> have experience with cache tiering or bcache. >> >> Thanks, >> Benjamin >> >> From: Arne Wiebalck [mailto:Arne.Wiebalck at cern.ch] >> Sent: Tuesday, July 08, 2014 11:27 AM >> To: Somhegyi Benjamin >> Cc: ceph-users at lists.ceph.com >> Subject: Re: [ceph-users] Using large SSD cache tier instead of SSD >> journals? >> >> Hi Benjamin, >> >> Unless I misunderstood, I think the suggestion was to use bcache devices >> on the OSDs >> (not on the clients), so what you use it for in the end doesn't really >> matter. >> >> The setup of bcache devices is pretty similar to a mkfs and once set up, >> bcache devices >> come up and can be mounted as any other device. >> >> Cheers, >> Arne >> >> -- >> Arne Wiebalck >> CERN IT >> >> On 08 Jul 2014, at 11:01, Somhegyi Benjamin < >> somhegyi.benjamin at wigner.mta.hu<mailto:somhegyi.benjamin at wigner.mta.hu>> >> wrote: >> >> >> Hi James, >> >> Yes, I've checked bcache, but as far as I can tell you need to manually >> configure and register the backing devices and attach them to the cache >> device, which is not really suitable to dynamic environment (like RBD >> devices for cloud VMs). >> >> Benjamin >> >> >> >> -----Original Message----- >> From: James Harper [mailto:james at ejbdigital.com.au] >> Sent: Tuesday, July 08, 2014 10:17 AM >> To: Somhegyi Benjamin; ceph-users at lists.ceph.com<mailto: >> ceph-users at lists.ceph.com> >> Subject: RE: Using large SSD cache tier instead of SSD journals? >> >> Have you considered bcache? It's in the kernel since 3.10 I think. >> >> It would be interesting to see comparisons between no ssd, journal on >> ssd, and bcache with ssd (with journal on same fs as osd) >> >> James >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.ceph.com/pipermail/ceph-users-ceph.com/attachments/20140711/a56a30db/attachment.htm>
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